Nickel dihydroxide

Endpoint summary

Additional information

The terrestrial toxicology of Nickel has been subject of numerous reviews/ assessments. For example:

-         Canadian Environmental Protection Act, Priority Substances List Assessment Report, Nickel and its Compounds (1994)

-         WHO (1991). EHC 108. Nickel.

-         ECB (2008). EU-Risk Assessment Nickel and Nickel compounds. EU 3rd priority substance list.

-         OECD (2008). SIAP. Nickel and Nickel compounds.  

 

In OECD SIAP (2008) and EU-Risk Assessment (2008) the hazard of Nickel has been assessed extensively, taking bioavailability correction into account.

-A total risk approach was performed.

-As for the aquatic compartment, bioavailability models were used to normalize ecotoxicity data to sets of standard physicochemical conditions. For the soil compartment, relationships between cation exchange capacity (CEC) and chronic nickel toxicity were used to normalize the ecotoxicity data.

-Extensive chronic soil toxicity data sets exist for soil microbial processes, plants, andinvertebrates. This data set is, to date, the largest data set on a metal for soil.

-To reduce soil-type related impact on the determination of an HC5 (andsubsequently the PNEC) for a given soil, all data in the nickel soil ecotoxicity database were normalized to a set of standard soil properties, using the established CEC based models.

-A pH-dependent “ageing factor” has been developed and applied to the toxicity data (cf. also the Zinc SIAR) and was applied prior to CEC normalization.

- As for the aquatic system it was concluded that statistical approaches based on “reasonable worst case” abiotic factor combinations were not relevant. An Ecoregion approach has instead been developed based on 6 reference soil scenarios that represent typical soil conditions. These include agricultural and natural soils that exhibit wide ranges of textures, pH, and CEC. The Ecoregion approach was developed for conditions typically found in EU soils and its applicability for use in other jurisdictions should be evaluated on a case by case basis.The datasets for The Netherlands, Spain and Wales cover the representativerange of pH CaCl2, organic matter, clay and eCEC for Europe.

- Species mean values were used to establish a species sensitivity distribution (SSD), from which an HC5 was derived. The Predicted No Effects Concentration (PNEC) was derived as a function of the HC5 and an assessment factor (PNEC = HC5/Assessment Factor = 2). For each soil Ecoregion scenario, the HC5 was determined by full cross-species normalization approach resulting in HC5 values ranging from 8.6 mg Ni/kg in acidic sandy soils to 194.3 mg Ni/kg for alkaline clay soils. Based on the amount, the type and nature of chronic data on soil organisms, remaining uncertainty an Assessment Factor of 2 was chosen for the soil nickel effects data set in its present status.

When an AF of 2 is taken into account, only 1 site from The Netherlands (out of 330) shows a RCR larger than 1 (RCR=1.2), while for Spain and England and Wales, 11.2 and 5.9% of the samples show RCR values larger than 1.

Secondary poisoning

In OECD SIAP (2008) and EU-Risk Assessment (2008) the hazard of Nickel has been assessed extensively.

Food Chains Modeled in Secondary Poisoning Assessment were:

seawater > mollusc > bird (oystercatcher)

seawater > fish / octopus / squid > mammal (harbor seal)

soil > earthworm > worm-eating bird / mammal (robin or starling / shrew)

For Avians "Generic" and "Species-specific" PNECs were derived

a) Generic:

Dietary NOECs = 150 mg kg-1 or 200 mg kg-1 (data for chicken and mallards, respectively)

Dietary PNEC/30 = 5.0 or 6.7 mg kg-1

b) Species specific:

-adjust based on the relative ingestion rate-to-body weight ratios for the mallard and species (i.e. oystercatcher or worm eating bird)

-lower assessment factor from 30 to 10

-Oystercatcher PNEC = 12.3 mg kg-1

-Worm eating bird PNEC = 8.5 mg kg-1

For mammalian again"Generic" and "Species-specific" PNECs were derived

a) Generic:

Dietary NOECs = 22 mg kg-1 wwt (data on rats)

Dietary PNEC/30 = 0.73 mg kg-1 wwt

b) Species specific:

-adjust based on the relative ingestion rate-to-body weight ratios for the rat and species (i.e. harbor seal, European otter or shrew)

-lower assessment factor from 30 to 10

-Harbor seal PNEC = 4.6 mg kg-1 wwt

-European otter PNEC = 2.3 mg kg-1 wwt

-Shrew PNEC = 0.12 mg kg-1 wwt

Conlusions:

None of the aquatic (marine or freshwater) food chains showed PEC/PNEC ratios greater than 1, and only two instances in the terrestrial food chains arose where the PEC/PNEC ratio was greater than 1. These instances were observed for the clay soil, for which the estimated PECoral was greater thanthe PNECoral for the shrew and for the worm-eating bird. Notably, using the highest calculated PECtotalregional nickel concentrations for freshwater and soil resulted in PEC/PNEC ratios below 1 for both mammalian and bird food chains.

Considering the cautious assumptions that were made in the assessment: 1. Interspecies variability varies ten-fold; 2. Bioavailability of soil to birds not accounted for; 3. Terrestrial birds eat only earthworms, and that the Ni contained in the soil (81 mg Ni kg-1) resulting in the highest PEC/PNEC ratios is of natural origin, a conclusion of no risk can be appropriately made for these soils as well. Acomprehensive local risk characterization has been performed for all point sources, i.e. local emission sites.

 

A critical soil nickel concentration of 60 mg Ni/kg was back-calculated from the PNECoral for shrews that feed on the mixed diet (worms plus isopods). Therefore, soils receiving anthropogenic nickel sources that give rise to soil nickel concentrations in excess of 60 mg Ni/kg may in theory be at risk for secondary poisoning. In the case of the Greek soil, the source of the nickel is known to be natural. Therefore, this soil would be removed from further consideration. This outcome is supported by the occurrence of shrews inwhere soil nickel concentrations are well in excess of 60 mg Ni/kg.

Soil databases from the UK and Spain were used in the Terrestrial Regional Risk Characterization There are soils within these databases that exceed 60 mg Ni/kg, which would indicate potential risk for the terrestrial secondary poisoning endpoints.

 

The source of the nickel in these soils therefore needs to be identified, which would also be the case for those soils within these databases that show conclusions of risk for direct nickel toxicity to soil dwelling organisms. Overall, however, there is no generic indication that concentrations above 60 mg Ni/kg occur at the regional level (e.g., the PECtotal regional values for nickel were, at the most, 35.8 mg Ni/kg).